Physical-chemical determinant properties of biological communities in continental semi-arid waters.

Throughout human history, water has undergone changes in quality. This problem is more serious in dry areas, where there is a natural water deficit due to climatic factors. The aims of this study, therefore, were (i) to verify correlations between physical attributes, chemical attributes and biological metrics and (ii) from the biological attributes, to verify the similarity between different points of a body of water in a tropical semi-arid region. Samples were collected every 2 months, from July 2009 to July 2011, at seven points. Four physical attributes, five chemical attributes and four biological metrics were investigated. To identify the correlations between the physicochemical properties and the biological metrics, hierarchical cluster analysis (HCA) and canonical correlation analysis (CCA) were applied. Nine classes of phytoplankton were identified, with the predominance of species of cyanobacteria, and ten families of macroinvertebrates. The use of HCA resulted in the formation of three similar groups, showing that it was possible to reduce the number of sampling points when monitoring water quality with a consequent reduction in cost. Group I was formed from the waters at the high end of the reservoir (points P1, P2 and P3), group II by the waters from the middle third (points P4 and P5), and group III by the waters from the lower part of the reservoir (points P6 and P7). Richness of the phytoplanktons Cyanophyceae, Chorophyceae and Bacillariophyceae was the attribute which determined dissimilarity in water quality. Using CCA, it was possible to identify the spatial variability of the physicochemical attributes (TSS, TKN, nitrate and total phosphorus) that most influence the metrics of the macroinvertebrates and phytoplankton present in the water. Low macroinvertebrate diversity, with a predominance of indicator families for deterioration in water quality, and the composition of phytoplankton showing a predominance of cyanobacteria, suggests greater attention to the management of water resources.

Water quality index calculated from biological, physical and chemical attributes.

To ensure a safe drinking water supply, it is necessary to protect water quality. To classify the suitability of the Orós Reservoir (Northeast of Brazil) water for human consumption, a Water Quality Index (WQI) was enhanced and refined through a Principal Component Analysis (PCA). Samples were collected bi-monthly at seven points (P1 - P7) from July 2009 to July 2011. Samples were analysed for 29 physico-chemical attributes and 4 macroinvertebrate metrics associated with the macrophytes Pistia stratiotes and Eichhornia crassipes. PCA allowed us to reduce the number of attributes from 33 to 12, and 85.32% of the variance was explained in five dimensions (C1 - C5). Components C1 and C3 were related to water-soluble salts and reflect the weathering process, while C2 was related to surface runoff. C4 was associated with macroinvertebrate diversity, represented by ten pollution-resistant families. C5 was related to the nutrient phosphorus, an indicator of the degree of eutrophication. The mean values for the WQIs ranged from 49 to 65 (rated as fair), indicating that water can be used for human consumption after treatment. The lowest values for the WQI were recorded at the entry points to the reservoir (P3, P1, P5, and P4), while the best WQIs were recorded at the exit points (P6 and P7), highlighting the reservoir's purification ability. The proposed WQI adequately expressed water quality, and can be used for monitoring surface water quality.

Investigação de variável adequada ao controle automático de vazão sem uso de sensores em campos irrigados por meio de análise multivariada / Investigation of variable appropriately to the automatic flow control without the use of sensors in fields irrigated by means of multivariate analysis

Utilizar inversores no controle de vazão de sistemas de bombeamento por meio da variação de sua velocidade pode ter uma maior viabilidade, caso o custo de sensores seja minimizado. Este trabalho investiga, por intermédio de análise multivariada, uma variável adequada ao pseudocontrole da vazão de um sistema de irrigação que economize o uso de sensores e simplifique o sistema de controle. Uma bancada de ensaio para coleta dados foi montada no laboratório e os dados foram processados no Statistical Package for the Social Sciences (SPSS). A análise de agrupamento hierárquico utilizando o método de Ward com base na distância euclidiana quadrática mostrou um grupo composto de quatro variáveis, estando presente nesse grupo a vazão, voltas no registro, altura do nível de água da calha parshall e a corrente elétrica, indicativo de que a corrente elétrica pode ser usada para o pseudocontrole, pois o inversor mede essa variável. A análise fatorial também indicou uma forte correlação da corrente elétrica com a vazão do sistema. A pressão foi o parâmetro da primeira componente da análise fatorial que apresentou a maior correlação com a vazão, no entanto o uso dessa variável para o controle automático demanda o uso de sensores.

Using inverters to control flow of pumping systems by means of changes in speed may be more viable if the cost of sensors is minimized. This work investigates through multivariate analysis an adequate variable for the pseudo control of the flow of an irrigation system that saves the use of sensors and simplifies the control system. A bench test to collect data was mounted in the laboratory and the data were processed using Statistical Package for the Social Sciences (SPSS). The hierarchical cluster analysis using the Ward method based on the squared Euclidean distance showed a group composed of four variables, being present in that group flow, turns on the register, water level of the Parshall weir and electric current, indicating that the electric current can be used for pseudo control because the inverter measures this variable. The factor analysis also indicated a strong correlation between the electric current and the system flow. In the first Principal Component, the pressure showed the highest correlation with the flow, although the use of this variable for automated control requires the use of sensors.

Similaridade da qualidade das águas superficiais da bacia do Curu, Ceará / Similarity of surface water quality at Curu watershed, Ceará, Brazil

Com a demanda de água crescendo a cada ano, é necessária uma maior atenção aos fatores responsáveis da qualidade das águas. Esta pesquisa teve como objetivo identificar a similaridade de variáveis determinantes da qualidade das águas do trecho perenizado da bacia do Curu, Ceará, durante a estação seca e chuvosa, pelo emprego de análise multivariada. As amostras de água foram coletadas em sete pontos (georreferenciados), nos meses de janeiro, março, maio e agosto de 2005, totalizando 28 amostras. Nas águas, foram analisados os seguintes atributos: pH, CE, Ca2+, Mg2+, Na+, K+, Cl-, CO3-, HCO3-, SO4-, PO4(3-), NH4- e NO3-. Quatro grupos homogêneos foram identificados, sendo estes independentes da posição geográfica dos pontos de coleta, demonstrando a maior influência da sazonalidade na definição da similaridade da qualidade dessas águas. Os valores da RAS (Razão de Adsorção de Sódio) definiram a dissimilaridade do grupo 1 em relação aos demais; já o grupo 2 foi definido pelo nitrato e fósforo; enquanto que os valores da Condutividade Elétrica (CE) e da RAS, os íons sódio e o cloreto determinaram a dissimilaridade entre os grupos 3 e 4. Embora as águas dessa área sejam inadequadas ao consumo humano, CE>0,5d Sm-1, o cloreto e o sódio não representam riscos à saúde humana. Com relação aos parâmetros determinantes para irrigação, em apenas um grupo a salinidade apresentou restrição ligeira a moderada, enquanto a RAS apresentou a mesma restrição em todos os grupos.

A special attention should be devoted to the water quality determinant factors, since the water supply has been decreased each year. The aim of this research was to define the similarity of determinant variables of water quality in the perennialized part of the Curu watershed, Ceará, Brazil. Multivariate analysis/Cluster Analysis was used for this investigation and it was proceeded during the wet and dry season. The samples were took in seven stations, spreading out along the rivers during four campaigns of collection (January, March, May and August of 2005), totalizing 28 samples. The water attributes analyzed were: pH, Ce, Ca2+, Mg2+, Na+, K+, Cl-, CO3-, HCO3-, SO4-, PO4(3-), NH4- and NO3-. Four homogeneous groups were identified. They were independent of their geographic position. They were identified expressing the influence of weather seasonality. The values of Sodium Adsorption Ratio (RAS) defined the dissimilarity of group 1 in relation to the others. The values of nitrate and phosphorus defined the similarity of group 2; while the Electric Conductivity (CE), RAS, sodium and chloride ions determined the non homogeneity between groups 3 and 4. Although the salinity level of water (CE>0,5d Sm-1) was not suitable to human consume, the Na+ and Cl- concentration do not present risks to human health. In relation to irrigation, only one group presented salinity risk from low to moderate, while SAR showed the same risk level for all groups.

Impacto da lixiviação de nitrato e cloreto no lençol freático sob condições de cultivo irrigado / Nitrogen and chloride impact on water table under irrigated condition

Os impactos ambientais provocados pelos fertilizantes nitrogenados, pesticidas e sais presentes nas áreas irrigadas vêm se tornando uma preocupação crescente, uma vez que estes podem se mover no solo desde a zona radicular até atingirem águas subterrâneas. Esta pesquisa teve como objetivo identificar a influência do manejo da irrigação e das chuvas sobre a dinâmica dos íons cloreto e nitrato ao longo dos perfis dos solos, bem como o seu impacto nas águas do lençol freático do Distrito Irrigado do Baixo Acaraú - DIBAU, Ceará. As amostras de solo foram coletadas a cada 50cm de profundidade, da superfície até a zona de saturação do lençol freático (7m) em duas áreas distintas, sendo uma irrigada com a cultura do coco (S1) e a outra uma mata nativa (S2). As amostras dos solos foram realizadas em período de plena atividade da irrigação (nov/06) e ao final da estação chuvosa (mai/07). As medições dos níveis e as coletas de água do lençol freático foram efetuadas, mensalmente, em quatro poços rasos, sendo dois inseridos na área irrigada e dois na área de mata nativa, no período de dez/2003 a nov/2005, nos meses de nov/2006, março e abril/2007. As maiores concentrações de cloreto nos perfis dos solos foram registradas durante a estação chuvosa, sugerindo a influência das chuvas no aporte de cloreto oriundo de aerossóis de sais marinhos. Já as maiores concentrações de nitrato ocorreram durante o período da irrigação. Os resultados também mostraram um aumento preocupante dos teores de nitrato nas águas dos poços influenciados diretamente pela agricultura irrigada, variando de 1,52 a 19,3mg L-1, excedendo significativamente os limites máximos aceitáveis pela Portaria n° 518/2004 para consumo humano e pela Resolução 357/05.

Environmental impacts of nitrogenous fertilizers, pesticides and salts contained in irrigation are becoming an increasing concern, because they may move with soil water from root zone to groundwater. The aim of this research was to identify the irrigation management and the rainfall depth influence over nitrate and chloride concentration in the soil profiles, as well as the risk of water table pollution in the Irrigated District of Baixo Acaraú (DIBAU), Ceará, Brazil. Soil samples were taken each 50cm deep soil profiles until to saturated zone (7m) in two different types of land use: irrigated area (S1) and native area (S2). Samples occurred during irrigation activities (Nov/06) and rainfall season (May/07). The water table was measured, monthly, from Dec/2003 to Nov/2005, Nov/2006, Mar and April/2007 in four shallow wells, two located in irrigated fields and the others in native. The greatest chloride concentration in the soil profiles was registered during rainfall season, suggesting the effect of sea-salt aerosols influence on chloride soil content. The greatest nitrate concentration occurred under irrigation period. Also, the results show that irrigation caused the groundwater concentration of NO3-N to increase from 1.52 to 19.3mgL-1, thereby, exceeding the standards on Regulation MS number 518/2004 and 357/2005 Resolution.